It is not clear how the footage was obtained, however, the leak was posted by "teapotuberhacker" on the GTA Platforms. The user also claims to be behind the recent network breach that targeted Uber. The hacker has also threatened to release more data, including source codes, assets, employee data, etc.
The gameplay videos are real, as confirmed by a Bloomberg reporter.The leaked videos have characters and features that GTA VI plans to include in the release version of the game. The videos are available on YouTube, Reddit and Twitter.According to The Verge, the development build can not be older than two years as the footage appears to be running on RTX 3060 Ti and RTX 3080 cards. GTA VI is apparently two years away from release, and the leaked videos are from its development and test stages.